1. Field of the Invention
The present invention relates to an electron-emitting device, an electron beam in which a number of electron-emitting elements are arranged, and a method for forming an image-forming apparatus such as a display constituted by using such an electron source. More specifically, the present invention relates to a method for manufacturing an electron emitting-device comprising a substrate, a pair of electrodes formed on the substrate, and a film having a narrow gap and connected between the electrodes.
2. Related Background Art
Conventionally, as electron-emitting devices, two kinds of devices, i.e., a heat electron-emitting device and cold cathode electron-emitting device are known. The cold cathode electron-emitting device is divided into electrical field emitting type, metal/insulator/metal type and surface conduction electron-emitting type.
A construction and manufacturing method for the surface conduction electron-emitting device is disclosed in Japanese Patent Application Laid-open No. 7-235255 and Japanese Patent No. 2903295.
Now, the surface conduction electron-emitting device disclosed in the above documents will be briefly explained.
As shown in a sectional view of FIG. 8, the surface conduction electron-emitting device includes a pair of opposed device electrodes 2, 3 disposed on a substrate 1, and a conductive film 84 connected between the electrode and having an electron-emitting region 85.
The electron-emitting region 85 includes a portion which is formed by fracturing, deforming or deteriorating a part of the conductive film 84 and in which a gap is formed, and deposits 86 mainly including carbon and/or carbon compound are formed on the conductive film within and near the gap by processing called as “activation”. Incidentally, the deposits are configured to be opposed to each other with a gap portion narrower than the aforementioned gap.
The activation processing is effected by continuing to apply pulse-shaped voltage to the device for a predetermined time period in an atmosphere including organic substance. In this case, as the shape shown in FIG. 8 is formed, current (device current If) flowing through the device and current (emission current Ie) emitted into vacuum are increased greatly, thereby obtaining a better electron-emitting property.
By using an electron source in which a plurality of the above-mentioned electron-emitting devices are formed and by combining such an electron source with an image-forming member comprised of fluorescent substance, an image-forming apparatus such as a flat display panel can be constituted.
On the other hand, Japanese Patent Application Laid-open No. 9-237571 discloses a method for manufacturing an electron-emitting device, comprising, in place of the activation processing, a step for coating organic material such as thermosetting resin, electron beam negative resist or polyacrylonitrile on a conductive film and a step for effecting carbonizing.
However, in the above-mentioned device, it is inevitable to use a step (called as “forming”) for forming a gap by energizing the conductive film, and material and thickness of the conductive film are selected so that the forming can be achieved preferably.
More specifically, in order to reduce an electric power required for the forming and to produce a good gap, it has been proposed to use a fine particle film of palladium oxide as the conductive film.
In addition, since it is difficult to obtain adequate electron emission by means of the gap formed by the forming, there has been a technique in which carbons or carbon compounds are opposed with each other with a narrower gap portion within the gap formed by the forming, by effecting the above-mentioned activation processing or the processing for coating organic polymer film and for effecting energization.
Accordingly, the conventional devices arise the following two problems:    1) When the fine particle film is used as the conductive membrane, it is not always easy to form the thickness and material of the film with high accuracy, and, thus, when a number of electron-emitting devices such as a flat display panel are formed, uniformity may be reduced.    2) Since additional steps such as a step for creating the atmosphere including organic substance and a step for forming polymer film on the conductive film with high accuracy are required for forming the narrower gap portion having good electron-emitting property, management of the steps becomes complicated.
To solve the above problems, there has been requested an electron-emitting device and a method for manufacturing such a device, in which device manufacturing processing can be simplified and an electron-emitting property can be improved.